Ion implantation is a process of depositing chemical species into a substrate by direct bombardment of the substrate with energized ions. In semiconductor manufacturing, ion implanters are used primarily for doping processes that alter the type and level of conductivity of target materials. A precise doping profile in an integrated circuit (IC) substrate and its thin-film structure is important for proper IC performance. To achieve a desired doping profile, one or more ion species may be implanted in different doses and at different energies.
In some ion implantations processes, the desired doping profile is achieved by implanting ions in the target substrate at high temperatures (e.g., between 150-600° Celsius). Heating the target substrate can be achieved by supporting the substrate on a heated platen during the ion implant process. A typical heated platen may include one or more heating elements, such as a metallization layer connected to a power source via electrical contacts. During operation, these electrical contacts may absorb some of the heat from the metallization layer, effectively acting as small heat sinks that can reduce the temperature of the heated platen in localized areas adjacent to the electrical contacts. As will be appreciated, any temperature variation between portions of the heated platen may affect the uniformity of the heat transferred to the target substrate, which in turn can adversely affect the ion implantation process. In some instances, such temperature variations can cause the heated platen to warp, bow, or even crack.
In view of the foregoing, it will be understood that there is a need to ensure that heat losses via electrical connections in heated platens are minimized in order to ensure substantially uniform platen temperature.